Molar Mass Calculator

Molar mass and mass percentages from a chemical formula, including brackets and hydrates.

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Formula

Chemical formula

Capital letters matter: Co is cobalt, CO is carbon monoxide. Brackets, hydrates with · or * (CuSO4·5H2O) and charges written like SO4^2- are fine.

Try one

Molar mass

CuSO₄·5H₂O

249.68g/mol

Before rounding: 249.677 g/mol
Rounded to: 2 decimal places, like the least precise atomic mass used (S 32.06)
Also written: 249.68 g mol⁻¹, or a formula mass of 249.68 u

Breakdown by element

Atoms, atomic mass, subtotal and mass percentage of each element
Element	Atoms	Atomic mass (g/mol)	Subtotal (g/mol)	Mass %
CuCopper	1	63.546	63.546	25.45%
SSulfur	1	32.06	32.060	12.84%
OOxygen	9	15.999	143.991	57.67%
HHydrogen	10	1.008	10.080	4.04%
Total	21		249.677	100.00%

Grams and moles

Mass (g)

Amount (mol)

10 g of CuSO₄·5H₂O is 0.04005 mol, about 2.412 × 10²² molecules or formula units.

moles = mass ÷ molar mass = 10 ÷ 249.68

How it’s calculated

Add up the atomic mass of every atom in the formula. Numbers after a bracket multiply everything inside it, and a number after · multiplies the part that follows.

1 × 63.546 + 1 × 32.06 + 9 × 15.999 + 10 × 1.008
= 249.677 g/mol

Mass % = subtotal ÷ molar mass × 100. Moles = mass ÷ molar mass, and one mole holds 6.022 × 10²³ particles (Avogadro’s number). Atomic masses are IUPAC standard values, the same as in the periodic table.

Molar Mass Calculator

Formula

Molar mass

Breakdown by element

Grams and moles

How it’s calculated

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